Transformer



R. L. OSBORNE TRANSFORMER Aug. 23, 1927. 1,639,662

' Filed July 7, 1922 fiber? L. 0 9602719 $3 4 ,g, 2. dummy avoided and produces a secondar Patented Aug. 23,1927. I

UNITED STA ROBERT L. OSBORNE, OIIOUNT CLEMENS, MICHIGAN, ASSIGNOR TO DONGAN ELEG "res PATENT OFFIC TIBJC MANUFACTURING G O., OF DETROIT, MICHIGAN, A COBPOBATION'OF MICHI- GAR.

ramsronunn.

Application filed. m 7 1922. Serial No. 573,307.

This invention relates to transformers for electric current, more particularly forcurrent of ,a radio frequency type; and the object is to provide a transformer for use in the receiving circuits of radio hones in which eddy currents are practical y avoided and to reduce what is termed the static effectZ. Further,-it is the object to provide a' transformer adapted for use in radio receiving circuits as a tuningelement whereby the receiving system is tuned by varying the inductance rather than by variation in ca acityas has heretofore been the practice.

reviously, transformers have been used in receiving circuits which are made up of a laminated iron core but the use of such previous transformers has induced or produced a distortion of the wave form of the secondary circuit which results-in a blurring of the sound wave emanating from the receiver. This blurring is often attributed to static effects which are 'Jnultiplied by the usual form of'transformer and this invention seeks to providea trans-former for current of radio frequency type in which the undesirable features of the usual laminated iron core transformer above mentioned are current whose wave. form is not distorte through influence of eddy currents in the transformer. I have found by providing an iron core for the transformer, which is made up of strips of extreme thinness or of articles of iron, eddy currents are practical y. eliminated and further have found that by varying the position of the' core relative to the rimary and secondary coils the system may be tuned with far greater ease and excellence of results than with previous. known types i in which- V Fig. 1 is a longitudinal section of a transof transformers. The various objects and several novel features of my invention are hereinafter more fully described and claimed; and the preferred form of construction ofa transformer embodying my invention is shown in the accompanying drawing former embodying my invention. F Fig. 2 is a section taken on line 2-'2 of i 1. I. i Fig. 3 is a diagram showing-the usual radiophone receiver circuit with my transxfor'mer'positioned therein between the first and second lamps.

i Fig. 4 is a section showing an alternfive form of core for the transformer. i Preferably the transformer is made substantially as shown in Fig. 1 and consists of a case 1 of non-magnetic material aper-v tured at one end for a rod 2 preferably of hard rubber or other non-magnetic material.

he case may be made of hard rubber or fiber or the like and is further provided with a cap 3 for the end thereof, which cap may, conveniently carry a cylindrical'or tubular extension 4. Onthis extension is wound the secondarycoil 5 which is in the form of two N coils '5, 5 each wound in a groove provided therefor. The primary coil 6 is wound in a groove thereon, between the two secondary coils and a cover 7 of insulating material may be placed on the outside of the coils.

The cap may be secured in' position bya pair of screws 8, 8 and there are two terminals 9. and 10 for the secondary coil and two terminalsll and 12 for the primary coil as will be understood from Fig. 2. These terminals may providebinding posts extending outward through the cap and provided with the nuts 13 toia'ttach the .cirf cuit wires thereto. A core for this coil is indicated at 14 and is formed of a multitude of very fine strips of soft metal held in a case or shell 15 of insulating or non magnetic material which is tubular in form and provided with a closure 16 atithe forward end. The rod 2 is preferablyintegral with the shell Iii-providing a closure for the opposite end. This rod 2 rides 'in the bearing "18 provided in-theend of the case 1 and a spring-pressed ball 20 is provided at the end of the bearing and engages the rod g 2. The core may be moved into or out of the shell or coilmanually and the ball 20 holds the core in its set position due to its engagement with the rod 2. As is well understood, the inductance is increased as the metal within the influence of the coilis .in-

creased and decreasedby withdrawing the j metal from the coil.

.An alternative form of construction 'is v shown in Fig. 4 in' which/the iron of the core is in the formof very fine particles of' iron held in the tube 15". of non-magnetic material and secured therein by an end plug and rod as in the form of core shown In- Fig. 1. In both these cores the iromisin a very finely divided form so that there 1s very little iron in any one mass thus ractically eliminating eddy currents whic occur when the iron is in larger masses, the tendency of which is to distort thesecondary wave form.

The structure is simple and inex nsive in character and-the core is readil a justed in position whereby the best resu t may be secured in the receiver circuit. The receiver circuit is not material as to its exact form and arrangement and the diagram Fig. 3 is iven as one instance of a circuit in which t is transformer is adapted for use and consists of the usual loop aerial 21, variable condenser 22, potentiometer 23, the telephone receivers 24, the lamps or bulbs 25 and 26, andthe usual connections with th batteries A and B.

My transformer is indicated diagrammati cally at 27, the'primary coil being connected on one side with the plate'ofthe first bulb and the receiver and battery on the other side while the secondary is connected with the loop on one side and grid of the second bulb on the other side. This secondary current is therefore an'amplification of the current passing through the primary and this is again amplified in passing through the bulb 26 to the receiver.

The principal features of the invention, as

are hereinafter set forth in the claims, are 1 involved in the construction of the trans former with a movable core to vary the inductance of'the circuit for the purpose of tuning; A further feature resides in providing the 'iron of the transformer in finely divided form, either the elongated type of Fig. 1 or the dust like type of Fig. 4. In Fig. l the particles are in the form of flat strips of the thinness of about. twothou sandths of an inch and in either arrangement the iron is practically uniformly distributed throughout the area of the core so that the area of. the iron at anypoint of cross section is uniform with that at any other point. Having thus full described my invention,

' what I claim and esire to secure by Letters Patent of the United States is-- 1. In a radio frequency transformer, 9.

a second shell of similar material supportedtherewithin, the axes of the shells coinciding, a secondary coil consisting of two coil parts in spaced relation on the second shell, a primary coil positioned centrally between the secondary coils on the second shell, an iron core in the second shell consisting of a mass of iron in finely divided state, a stem of non-magnetic material for the core extending through one end of the outer shell,

spring means engaging the stem, the core and stem being movable on the axis of the two shells and. held in adjusted posit-ion by the spring, a removable closure member for the outer shell, and-terminals for both the primary and secondary coils secured to the said closure member.

- 3. In a radio. frequency transformer, a shell of non-magnetic material on which the secondary coil is wound in a plurality of spaced coiled parts, a primary coil wound on the shell in a position intermediate the secondary coil parts with substantially equal -.port1ons of the secondary coil on opposite sides of the primary coil, an iron-core 1n the second shell consisting of a mass of lI'OIl in non-homogeneous form, the area of iron atany point .of cross section being. practically umform with that at any other point, and means for adjustably positioning the iron core relative to the coils.

In testimony whereof, I sign this specification. it

, ROBERT L. OSBORNE. 

